1. Field of the Invention
The present invention relates to an extruder and a cylinder exchanging method thereof.
2. Description of the Related Art
In a small-sized extruder used for various experiments, cylinders are frequently disassembled and reassembled. Accordingly, the extruder must have a structure which is capable of easily disassembling and reassembling the cylinders. As a method of assembling the cylinders, there is a provided a method of providing flanges on the both ends of the cylinders and fastening the flanges using a plurality of bolts. However, this method is not suitable for the small-sized extruder for experiment. When the flanges are fastened using the bolts, the plurality of bolts must be exchanged. Accordingly, this method is not suitable for the extruder for experiment in which exchange is frequently performed. In addition, when the flange is provided, the size required for attaching a heating source (heater), a devolatilization device (vent) or a feeding device (side feed) cannot be ensured.
Accordingly, the small-sized cylinders are generally fastened using a tie bar bolt fastening method of fastening all the cylinders without using the flanges.
FIG. 8 to 10 are front views and side views showing an intermediate cylinder, a vent cylinder and a side feed cylinder of a related small-sized twin-screw extruder in which a flange is not provided, respectively, each of which A is the front view and B is the cross-sectional side view.
In an intermediate cylinder 110 shown in FIG. 8, a screw receiving portion 100 having a cross-sectional shape in which two circular arcs communicate with each other and a drill jacket 101 surrounding the screw receiving portion are provided. Positioning pin holes 102 and tie bar bolt holes 103 are formed in the outside of the drill jacket 101. In a vent cylinder 111 shown in FIG. 9, vent holes 113 are formed in addition to the above-described configuration. In a side feed cylinder 112 shown in FIG. 10, side feedholes 114 are formed. These cylinders are held together by a bolt 104, passing through the tie bar bolt hole 103. In addition, an unillustrated heater is attached to each of the cylinders.
However, in the extruder having the configurations shown in FIGS. 8 to 10, the cylinder needs to be moved in the axial direction of the positioning pin 105 until the positioning pin 105 is pulled out of a corresponding positioning pin hole 102 when the cylinder is exchanged as shown in FIGS. 11A-11B. For the movement in the axial direction of the positioning pin 105, a space for pulling out the exchanged cylinder need be ensured by moving the other cylinders as well as the exchanged cylinder in the axial direction.
JP-A-07-266405 discloses an extruder capable of exchanging a cylinder without moving the cylinder in an axial direction of a pin. In the cylinder of this extruder, two grooves are formed in a lower surface and tie rods are inserted into the two grooves to position the cylinder. By this configuration, the cylinder can be pulled upward and exchanged.
In the extruder having the configuration disclosed in JP-A-07-266405, seven segment barrels including segment barrels 4(A) to 4(G) are connected. In each of the segment barrels, two through-holes, through which tie rods 10 penetrates as well as cutout grooves 13 are formed. The tie rods 10 are not only fitted into the cutout grooves 13 but also inserted into the through-holes from the segment barrel 4(G) side. Accordingly, when the segment barrels 4(B) to 4(G) except the segment barrel 4(A) are exchanged, the tie rods inserted into the through-holes of the segment barrels which are not directly associated with the exchange must be also pulled out. Thus, after the segment barrel is exchanged, it is necessary to position the other segment barrels which are not directly associated with the exchange and to insert the tie rods 10 into the other segment barrels.